1. Field of the Invention
This invention relates to logging equipment and, more particularly, to devices for delimbing trees after the trees have been harvested.
2. Brief Description of the Prior Art
Tree delimbing, following the felling, or harvesting, of a tree historically has been done manually with the aid of a chain saw. For larger timber, and particularly for fir and spruce, when a tree is felled, the weight of the tree will cause many of the limbs to snap off the trunk; and the yarding or skidding of the felled tree to a landing would also cause more of the limbs to snap off under the weight of the tree. Consequently, when the felled tree reached the landing, the manual removal of the remaining limbs by means of a chain saw was convenient and, relatively-speaking, not too dangerous. For smaller timber, and particularly for pine--which tends to be bushy--when a tree is felled, the weight of the tree is not sufficient to cause many of the limbs to snap off the trunk; and the yarding or skidding of the felled tree to a landing would also not cause many of the limbs to snap off because of the relative lightness of the tree. Moreover, because such a smaller tree, or a tree that is particularly bushy such as pine, would arrive at the landing, essentially supported by its limbs, and with essentially all of its limbs intact, the task of manually removing the limbs by means of a chain saw would be much more hazardous and also would be much more time consuming and economically unproductive.
There has arisen, therefore, a class of devices known as "delimbers" which are designed to delimb a whole tree at the landing site, thereby either eliminating the requirement for manual delimbing by means of a chain saw or drastically reducing the time that a logger must spend in manual delimbing. In particular, where modern forestry practice is necessitating the removal of smaller trees to thin-out a forest, there is an even more growing need for delimbing devices that will delimb whole, felled trees by machine.
A popular type of delimbing device has come to be known as a pull-through delimber. A pull-through delimber is intended to be operated in conjunction with a grapple-type log loader. The delimber will be set near such a log loader so that the trunk of a tree to be delimbed can be grasped by the loader grapple and placed astride the delimber. The delimber will have some means to encircle the log with delimbing devices, and the delimbing devices will be caused to encircle the log placed therein by the grapple loader. The grapple loader, without letting loose of the log, will then strip the tree trunk through the delimber, and the delimber devices will strip the trunk of the tree's limbs. The grapple loader will then, again without releasing the tree trunk, position the stripped trunk alongside the loader and release it.
The pull-through delimbers available today have become so expensive that many logging operators cannot afford them. Moreover, many of these delimbers have become so complicated, by the addition of tree trunk-bucking and tree-topping equipment for example, as to have become even more expensive, and more susceptible to damage--and thus subject to expensive downtime--and more susceptible to jam-ups, and operator inefficiencies; hence more expensive to operate.